This invention concerns novel monodisperse or polydisperse compounds, which can be monomeric or oligomeric, and which, e.g., are based on ornithine, lysine, diaminobutyric acid, diaminopropionic acid, aminoethylglycine or other amino acids or peptides and analogues thereof, and which contain substituted or unsubstituted azobenzenes or other physically functional groups, e.g., photoresponsive groups, as side chains and, if desired, in combination with other functional ligands or side chains. In particular, the invention is directed to materials comprising such compounds used for optical storage and processing applications.
Polymers containing photoresponsive functionalities appear promising as future materials for optical storage of information. In particular, liquid-Mrystalline polymers (Eich, M., Wendorff, J. H., Reck, B. and Ringsdorf, H. Makromol. Chem. Rapid Commun. 8, 59-63 (1987); Eich, M. and Wendorff. J. H., Makromol. Chem. Rapid Commun. 8, 467-471 (1987); Wiesner, U., Antonietti, M., Boeffel, C. and Spiess, H. W. Makromol. Chem. 191, 2133-2149 (1990); Gibbons, W. M., Shannon, P. J., Sun, S.-T. and Swetlin, B. J. Nature 351, 49-50 (1991); Stumpe, J., Muller, L., Kreysig, D. Makromol. Chem. Rapid Commun. 12, 81-87 (1991); Hvilsted, S., Andruzzi, F. and Ramanujam, P. S. Opt. Lett. 17, 1234-1236 (1992); Xie, S., Natansohn, A and Rochon, P. Chem. Mater. 5, 403-411 (1993); Hvilsted, S., Andruzzi, F., Kulinna, C., Siesler, H. W. and Ramanujam, P. S. Macromolecules 28, 2172-2183 (1995)) and photorefractive polymers (Ducharme, S., Scott, J. C., Twieg, R. J. and Moerner, W. E. Phys. Rev. Lett. 66, 1846-1849 (1991); Liphardt, M., Goonesekera, A, Jones, B. E., Ducharme, S., Takacs, J. M. and Zhang, L. Science 263, 367-369 (1994); Meerholz, K., Volodin, B. L., Sandalphon, Kippelen, B. and Peyghambarian, N. Nature 371, 497-500 (1994)) have been the focus of considerable attention.
The known art in the area of optical storage has been concentrated on polymers either doped with dyes or with dyes covalently attached to them. Previous work in this area has been described in several articles; Eich, M. and Wendorff, J. H., J. Opt. Soc. Am. B 7, 1428-1436 (1990); Xie, S., Natansohn, A and Rochon, P., Chem. Mater. 6, 403-411, (1993), Hvilsted, S., Andruzzi, F., Kulinna, C., Siesler, H. W. and Ramanujam, P. S., Macromolecules, 28, 2172-2183 (1995). Most earlier work has been centred around molecules that need to be aligned either by rubbing or poling with electric fields. As discussed by Xie et al. and Hvilsted et al. it is also possible to store on thin films of organic materials which need no prealignment of the molecules. Erasure of information can be performed either by means of light or heat. Diffraction efficiencies in these films have been of the order of 50-60%. Recently, nearly 100% diffraction efficiency has been achieved in a photorefractive composite polymer film (Meerholz, K, Vblodin, B. L., Sandalphon, Kippeln, B. and Peyghambarian, N., Nature, 371, 497-500 (1994)). The composite film used in that application was made up of the following compounds: 2,5-dimethyl-4-(p-nitiophenylazo)anisole, poly(N-vinylcarbazole), 2,4,7-trinitro-9-fluorenone, N-ethylcarbazole. The maximum diffraction efficiency of 86% was achieved when an electric field of 90 V/mm was applied over the film. However the grating efficiency dropped to 15% of the maximum value within 24 hours after all the light beams and the electric field were switched off. Bieringer et al. have obtained a diffraction efficiency on the order of 90% in thick films of liquid crystalline side chain polymers with azochromophores. (Th. Bieringer, R. Wuttke, D. Haarer, U. Geoner and J. Rxc3xcibner, Macromolecular Chemistry and Physics, 196, 1375-1390 (1995)). As far as we are aware, the only instance of optical storage in peptides is the work of Cooper et al (Cooper, T. M., Tondiglia, V., Natarajan, L. V., Shapiro, M., Obermeier, K. and Crane, R. L., Appl. Opt. 82, 674-677 (1993)) on holographic grating in poly(spiropyran-L-glutamate). A diffraction efficiency of 0.02% was achieved at an incident energy at 488 nm of about 100 J/cm2, dropping to 0.015% 40 minutes after the recording.
EP 0474431 relates to amphiphilic compounds having a polyamide backbone carrying, e.g., molecular moieties made hydrophobic by attachment of a group containing from 8 to 40 carbon atoms. These compounds are used for forming optical elements for use in optical devices with non-linear optical (NLO) properties. These compounds may be organised into ordered arrays using the Langmuir-Blodgett technique. It is clear from the present description and claims that the organic compounds of the present invention does not include compounds having ligands carrying such hydrophobic moieties, in particular not C8-40 moieties.
The present invention in particular relates to organic compounds having a physical functionality which can be influenced by external stimulation, said compounds comprising one or more segments of the following formula G 
wherein Y is a linking group or a single bond; L is a physically functional group comprising one or more physically functiona ligand(s); and xe2x80x94Axe2x80x94Bxe2x80x94 designates a backbone moiety. The segment G is preferably included in a domain comprising a total of 2-25 segments where some of the segments may be segments of the following formula Gxe2x80x2
wherein the groups Axe2x80x2, Bxe2x80x2, and Yxe2x80x2 have the same meaning as defined for the groups A, B, and Y, respectively, and where the group Lxe2x80x2 designates a physically non-functional group comprising one or more physically non-functional ligand(s).
The present invention further relates to materials comprising or consisting of such compounds. These materials have excellent properties with respect to diffraction efficiency in relatively thin films and with respect to stability of the material even at temperatures as high as at around 150xc2x0 C.
The present invention also relates to the use of a material comprising an ensemble of the compounds, preferably monodisperse, for optical storage of information.
The invention further relates to the use of a material comprising an ensemble of compounds, preferably monodisperse, in nonlinear optics, as a photoconductor, as a photonic band-gap material, as an electrically conducting material, as an electroluminescent material, as a piezo-electric material, as a pyroelectric material, as a magnetic material, as a ferromagnetic material, as a ferroelectric material, as a photorefractive material, or as a material in which light-induced conformational changes can be produced.
The invention further relates to a process for optically storing information comprising irradiaton of an optically isotropic area of a material of monodisperse or substantially monodisperse compounds with polarised light, thereby forming an optically anisotropic phase in the irradiated area of the film.